Wheel rim locking device for tyre removal machines

ABSTRACT

A wheel rim locking device for tire removal machines, comprising, for supporting the wheel rim, an upper plate provided with an axial hole and supported at the top of a hollow vertical rotary shaft, conical means to be inserted axially into said hole and into the cavity of said shaft to lock the wheel rim in a centered position, means driving said conical means towards the wheel rim and axially locking them, and means for rotatably locking said hollow shaft relative to said wheel rim.

[0001] This invention relates to a self-centering device for locking the wheel rim for the purpose of mounting or removing its tire.

[0002] To lock the wheel rim in the working position, tire removal machines are currently provided with suitable devices, known as self-centering devices, which generally comprise a circular plate provided with a series of radial grooves within which slides comprising locking heads (fasteners) which lock the wheel rim in the working position are made to slide. The locking heads, generally four in number, are equidistant about a circumference, and are of the double acting radial sliding type, in order to be able to grip the wheel rim both from the outside and from the inside.

[0003] The circular plate is rotated about itself by a coaxial shaft driven by a suitable motor unit.

[0004] The slides are caused to slide within the grooves by a double-acting cylinder-piston unit positioned coaxial to the shaft and acting on levers connected to the slides, as described in greater detail in Italian utility model No. 224593 in the name of the same Applicant.

[0005] In mounting or removing a tire onto or from the wheel rim, only one side of the tire at a time can be operated on, i.e. after operating on one side of the wheel rim, this has to be rotated through 180°.

[0006] This both demands physical force from the operator and results in an extension of the operating time.

[0007] On the other hand, those systems which lock the wheel at the hub, and which allow access to both sides of the wheel at the same time, present the drawback of insecure wheel locking against rotation, which is often precarious.

[0008] The object of the invention is to overcome the drawbacks of the known art within the framework of a rational and reliable solution.

[0009] The invention attains said object by providing a device for locking the wheel rim at the hub, comprising means for rotating the wheel even if considerable tangential resistance forces are present.

[0010] Said object is attained by the invention by virtue of the characteristics stated in the claims.

[0011] The constructional and operational characteristics of the invention are highlighted in the ensuing detailed description, given with reference to the accompanying figures, in which:

[0012]FIG. 1 is a side view of the invention.

[0013]FIG. 2 is a section on the line II-II of FIG. 1.

[0014] The aforestated figures show the device 1 for supporting and locking the wheel rim 2.

[0015] The device comprises a shaft 3 rotated by known means, not shown, and which projects from the base 4 of the tire removal machine, also not shown.

[0016] With reference to FIG. 2, the shaft 3 supports at its upper end a circular plate 6, on which the wheel rim 2 is rested.

[0017] The plate 6 is provided with an axial hole and six equidistant radial grooves 61.

[0018] The plate 6 is also provided with an annular descending lower skirt 60, to the free end of which there is fixed a cover 7 which, together with said skirt 60, defines a chamber 8.

[0019] Within the chamber 8 there sealedly slides an annular piston 9, provided with a rod 90 sealedly mounted about the shaft 3.

[0020] A part of the shaft 3 is axially hollow, the cavity being of hexagonal cross-section.

[0021] Within the wall of the hollow rod 90 there is present a conduit 91 through which a pressurized fluid is fed above the piston 9.

[0022] Between said piston 9 and said cover 7 there is interposed a spring 10 which maintains the piston 9 urged upwards.

[0023] The rod 90 of the piston 9 comprises a U-shaped external pawl, which rocks about two externally projecting diametrical pins, and is provided with a central tooth 110 which enters the interior of said hollow shaft 3 via apertures 30 and 92, by passing through said rod.

[0024] A bar 130, of hexagonal cross-section, pertaining to a device 13 for locking the wheel rim 2 in the working position is received in the interior of said hollow shaft 3.

[0025] The bar 130 comprises annular projections 137 which are upperly flat and lowerly conical, so that when the bar is inserted into the hollow shaft 3 the conical part of the projections causes the pawl 11 to rotate against the action of a leaf spring 14, while at the same time the bar is unable to be withdrawn because the leaf spring maintains the pawl 11 above the upper flat surface of said projections 137.

[0026] The bar 130 is inserted into the hollow shaft 5 until the cone 132 encounters the outer surface of the central hub 21 of the wheel rim 6.

[0027] The device 13 comprises an upper member 131 from which said bar 130 descends and to which a locking cone 132 coaxial with said bar 130 is fixed.

[0028] The member 131 also comprises a handle 133 within which there slides a bar 134, the free end of which carries a vertical sleeve 135 within which a second bar 136 slides.

[0029] When the wheel rim 2 is in position, the bar 130 is inserted into said hollow shaft 3, and the second bar 136 is positioned in one of the holes 20 by which the wheel rim 2 is fixed to the vehicle.

[0030] The hexagonal cross-section of the bar 130 and of the cavity of the shaft 3 ensure that the lower end of the bar 136 lies in one of the six radial grooves 62 present in the circular plate 62.

[0031] In this manner by lowering the bar 136, this becomes secured both to the bar 130 and to the plate 6, and can exert a large force to cause the wheel rim to rotate without undergoing deformation.

[0032] With the device rotatably blocked, compressed air is fed through the conduit 91 and the piston 9 descends against the action of the spring 10.

[0033] The descent of the piston also determines the lowering of the pawl 11, the tooth 110 of which rests against the flat upper surface of one of the annular projections 137, and remains locked in position by the action exerted by the leaf spring 14.

[0034] In this manner, the wheel rim 2 becomes definitively locked in the working position.

[0035] When the tire has been mounted on or removed from the wheel rim 2, the wheel rim is released by simply discharging the compressed air so that the spring 10 raises the piston 9 and the pawl 11, so that this disengages from the annular projection 137. 

1. A wheel rim locking device for tire removal machines, characterised by comprising, for supporting the wheel rim, an upper plate provided with an axial hole and supported at the top of a hollow vertical rotary shaft, conical means to be inserted axially into said hole and into the cavity of said shaft to lock the wheel rim in a centered position, means driving said conical means towards the wheel rim and axially locking them, and means for rotatably locking said hollow shaft relative to said wheel rim.
 2. A device as claimed in claim 1 , characterised in that said conical locking means comprise an axial cone with a bar provided with circumferential teeth and insertable into said shaft, within which said teeth engage a pawl which can be laterally inserted into the interior of said hollow shaft, and means for causing said pawl to move axially to said shaft, to lock said cone against said wheel rim.
 3. A device as claimed in claim 1 , characterised in that the upper plate of the rotary shaft comprises a descending cylindrical skirt within which there sealedly slides an annular piston provided with a hollow rod positioned about the outside of said shaft, said hollow rod being provided with an aperture through which said pawl acts, in a position corresponding with this aperture there being located in the wall of the hollow shaft an opening through which said pawl comes into contact with the teeth of the bar carrying the centering cone.
 4. A device as claimed in claim 3 , characterised in that the conduit which feeds compressed air onto the piston is provided within the wall of the hollow rod of the piston.
 5. A device as claimed in claim 1 , characterised in that the upper plate is provided with radial grooves, in one of which there engages the lower end of a locking bar slidable parallel to the plate axis within a seat rigid with the centering cone, said locking bar being inserted into one of those holes in the wheel rim which receive the wheel rim fixing bolts.
 6. A device as claimed in claim 2 , characterised in that the bar coaxial with the cone, and the shaft which is to receive it, have matching polygonal cross-sections so that they remain rotatably locked together.
 7. A device as claimed in claim 5 , characterised in that the polygonal cross-section has a number of sides equal to the number of grooves in the plate.
 8. A device as claimed in claim 6 , characterised in that the polygonal cross-section has a number of sides equal to the number of grooves in the plate. 